Semiconductor integrated circuit (IC) density and maximum frequency of operation increases every year. In recent years, the operating frequency of commercial communications and radar applications has also increased towards the upper end of the radio frequency spectrum, including operation at mm wavelengths. With the silicon chip assuming greater functionality at higher frequencies in a smaller area at a lower cost, it is becoming economically feasible to manufacture high-frequency wideband ICs for both commercial and consumer electronic applications. High-frequency wideband IC applications now include millimeter (mm) wave applications such as short range communications at 24 GHz and 60 GHz and automotive radar at 24 GHz and 77 GHz.
Several frequency bands in the millimeter wave range have been approved by the Federal Communications Commission (FCC) for wireless communications and automotive radar. These include the 24.05˜24.25 GHz and 57˜64 GHz bands for high speed wireless communications, and the 22˜29 GHz and 76˜77 GHz bands for automotive radar. The 76˜77 GHz band has also been allocated for use in automotive radar in many other countries around the world. The Electronic Communications Committee (ECC) within the European Conference of Postal and Telecommunications Administrations has allocated the 77˜81 GHz window for automotive ultra wide band (UWB) short-range radar. Although current industrial efforts in the 77 GHz range are focused on automotive radar, millimeter wave wireless systems can also be used for other applications, such as short-range surveillance, microwave imaging and ultra high-speed data transmission.
Mm-wave communication and radar applications are generally designed to have both high power output and a directional antenna to compensate for relatively high signal propagation losses in air. Phased array antennas can provide a robust solution to the challenges of high frequency (mm wavelength) power generation by increasing the effective isotropic radiated power (EIRP) due to their array gain, beam-forming, and electronic beam-steering properties. “A Fully Integrated 24-GHz Eight-Element Phased-Array Receiver in Silicon”, Xiang Guan, et. al., IEEE Journal of Solid-State Circuits, Vol. 39, No. 12, December, 2004, by two of the present inventors describes one such integrated solution using phased arrays.
A number of problems have been observed in high frequency mm-wave integrated applications. Coupling power output from an integrated mm-wave transmitter to an off chip radiating device, such as an off chip antenna, or directly from an integrated circuit emitter to propagation in air is particularly problematic. Losses related to such off chip coupling can include substrate dielectric loss, substrate conductive losses, voltage induced breakdowns, poor metal conduction to the chip, and unwanted signal radiation at the chip RF interface. Similar losses, with the exception of voltage induced breakdowns, are problematic when coupling mm-wave signals from the air to the input stages of an integrated mm-wave transceiver.
Another problem involves testing mm-wave integrated devices. High cost test setups, such as bench instrumentation found in R&D laboratories or automatic test equipment (ATE) as found at production facilities are generally not available for field use. It is often difficult to properly test and evaluate the performance of most integrated mm-wave applications in the field.
Therefore, there is a need for signal radiating solutions for integrated mm-wave applications that do not require high frequency off chip RF connections. There is also a need for built in test and measurement capabilities in integrated RF systems that can fully characterize both receiver and transmitter performance, including one or more antenna systems.